The invention relates to a detachable device for locking the mobile component of a contactor in its ON position put to a rest position by a return spring and closing the power contacts of the contactor in the ON position, the said device comprising the following in a box:
a coupling piece which is linked to the movements of the mobile component and which moves between an inactive position when the component is off and an active position when it is on;
a locking lever which is able to oscillate around a pivot between a position that is released when the coupling piece is inactive and an engaged position imparted to it by a spring when the coupling piece is active;
a bearing surface on which bears a roller placed at the free end of the lever when the latter is engaged so that it is under longitudinal compression; and
an unlocking electromagnet a mobile push rod of which works when it is energized, together with the locking lever to interrupt the thrust and give it its released position.
These locking devices are used when it is wished to maintain, for example, a contactor in its ON position without permanently energizing the electromagnet that closes the contacts. They then allow the said contactors to be activated by current pulses and thus to economise energy during the intervals between two pulses.
These locking devices are moreover very useful when it is desired to memorize the status of the switching devices of an installation when the power supply of their electromagnets is accidentally cut off and, for this reason, they allow the installation to be started up again under conditions identical to those that existed at the time of the breakdown; these devices are particularly advantageous when any safety circuits in such an installation have to be returned to service immediately after a breakdown.
Any detachable locking device which is fitted on a contactor must be able to maintain its switching components in an ON position at which the pressure between the contacts is appropriate, that is, the pressure between the fixed and mobile contacts must lie between figures that are close together and correctly determined.
This condition which is difficult to respect when the devices are fitted on contactors of the same type, because of the variety of manufacturing dimensions, becomes practically impossible to respect when the same locking device has to be adapted to apparatus of different types.
Such a difficulty appears particularly when the travel distances of the armatures of the contactor mechanisms are different as is the case with coils are fed with DC current and coils fed with AC current.